The present invention relates to a negative film carrier used for a photograph printing apparatus, and more particularly, to a negative film carrier for correctly sensing the DX code of a negative film.
FIG. 1 is a schematic diagram showing the overall structure and component layout of a conventional printer for use in photograph printing. Referring to FIG. 1, in the upper portion of a printer body 1, printing paper is wound on a roll 2, and a container 12 for enclosing roll 2 is provided. A tray 18 for receiving the printing paper after being cut into pieces by a cutter 17 installed adjacent thereto is provided in the upper portion of the other side of the printer body 1. Disposed along the path of the printing paper between container 12 and tray 18 is an exposing portion 13 and a processing portion 16. The exposing portion 13 is arranged vertically and located adjacent to an optical system (described below), to thereby expose the downwardly proceeding printing paper. The processing portion 16 is provided with a multitude of transfer rollers and processing chambers, for processing and fixing the exposed printing paper. In addition, a cavity 14 where the exposed printing paper stays temporarily is provided in the lower portion of exposing portion 13.
The optical system includes, aligned along a single optical axis OA, a light source 4 for generating light that exposes the printing paper, a color filter 5 for passing a specific wavelength of light emanating from light source 4, an optical diffusion box 6 for uniformly diffusing filtered light from color filter 5, and a table 7 positioned above optical diffusion box 6, for supporting a negative film carrier 8. Further, again along optical axis OA, an image forming lens 9 is provided above table 7, and a shutter 10 for controlling the passage of light from image forming lens 9 is provided above the lens. In addition, a mirror 11 for reflecting the light passed through shutter 10 along optical axis OA' toward exposing portion 13 is situated at the proper angle above the shutter.
In an actual exposure, the light generated from light source 4 passes through the negative film (hereinafter also referred to as "film") on film carrier 8 and forms image light. Then, the image light passes through image forming lens 9 and reaches printing paper 3 via mirror 11, thus forming an image on the printing paper. In the formation of the image on the printing paper 3 as above, the exposure time depends on the opening time (speed) of shutter 10.
As shown in FIG. 2, a negative film carrier 8 of the photo printing apparatus, film 20 is transferred screen-by-screen in a predetermined direction through a film path 22 so that the image of the film is reflected onto printing paper 3. A DX code portion 40 and a frame number code portion 42 are respectively formed in the side margins of film 20. Here, frame number code portion 42 includes bar-code data for marking each screen in numerical sequence.
FIG. 3 illustrates the DX code portion 40 of negative film 20 in more detail. DX code portion 40 is comprised of inner and outer bar-code portions for DX code timing marks 45 and DX code date 44, respectively. Here, the DX code data indicates the film's manufacturer, type, etc. A perforation 48 along the inner bar-code portion of film 20 is formed with a predetermined spacing throughout the length of the film. Frame number code 42 is comprised of a bar-code indicative of the number accorded to each screen of film 20.
Installed in negative film carrier 8 are a sensor for the DX code portion 40 and a sensor for the frame number code portion 42, which are respectively disposed on either side of film path 22. The DX code sensor comprises separate sensors for respectively detecting DX code data 44 and DX code timing marks 45 and performs a proper exposure and development processing based on the signal detected by the sensor for code data 44. Also, the exposure is performed for each screen based on the signal detected by the frame number sensor. The installed sensors each are fixed to a sensor holder for determining its location with respect to the negative film carrier.
As shown in FIG. 3, the overall width W of DX code portion 40 of film 20 is approximately 2.06 mm, with the width W1 for DX code data 44 of DX code portion 40 being in the range of 0.75 to 1.26 mm, which means that the bar-code markings must be confined to an extremely limited space. Meanwhile, as shown in FIG. 2, the film itself has a width of B of 35 mm with a tolerance of +0.0 mm and -0.2 mm. Here, it should be noted that the width C (FIG. 2) of film path 22 is set to a dimension somewhat larger than the width B so that film 20 can be smoothly conveyed.
Due to the above dimension requirements for marking the bar-codes in DX code portion 40 of film 20, the positioning of the DX code sensor, which is fixed to negative film carrier 8, is critical and must be precisely controlled. Otherwise, a crosstalk phenomenon occurs whereby the respectively detected outputs of the sensor for detecting DX code data 44 and the sensor for detecting DX code timing marks 45 coexist in one or both sensor outputs, or the DX code portion 40 is undetectable altogether.
However, according to the conventional negative film carrier, since each sensor is fixed to a sensor holder which determines a sensor location with respect to negative film carrier 8, the location of the sensor holder must be precisely adjusted with respect to film path 22 of the carrier. Also, a re-adjustment is necessary if the sensor is changed and whenever a repair is made to any of the related components, which is cumbersome. Moreover, as described above, since width C of film path 22 is set somewhat larger than width B of film 20, the negative film is allowed to move laterally, to the extent of the difference between width B and width C, which further contributes to the generation of crosstalk.